A fuel cell system described in, for example, Patent Literature 1 is a conventional fuel cell system having a function of discharging resultant water and gases. The fuel cell system of Patent Literature 1 is designed to be mounted to a vehicle and has such a structure that an anode off-gas from a fuel cell stack is introduced into a gas-liquid separator through an off-gas flow path. The anode off-gas contains unreacted hydrogen and resultant water. The gas-liquid separator incorporates an ion exchange filter which partitions the inner space of the gas-liquid separator vertically and a chamber below the ion exchange filter for holding a certain amount of resultant water.
Moreover, the fuel cell system circulates hydrogen separated by the gas-liquid separator to a hydrogen supply system of the fuel cell stack and also drains the resultant water separated by the gas-liquid separator to the outside by utilizing the pressure and flow speed of the hydrogen. In this way, the resultant water is prevented from flowing into the off-gas flow path when the vehicle is tilted.